The sequential development of morphological patterns in the visual system of the chick embryo is being studied to clarify temporal changes that may predispose to the formation of particular pathways, and to the organization of the retinotopic projection to the optic tectum. Death of ganglion has been recorded in the retina of normal chick embryos and more extensively in retinal areas which project to tectal regions that have been destroyed at 4-5 days of incubation. This work suggests that ganglion cells require central connections to survive, a finding that is consistent with the similar loss of cells from the retinas of eyes grown on the chorioallantoic membrane where they cannot form central connections. Ganglion cells that persist in areas of extensive cell loss after tectal lesions have sustaining, direct projections to non-tectal areas as determined by radioautographic and horseradish peroxidase tracing methods. Present interests are directed to the specification of retino-tectal connections and the geometry of the optic chiasm as it apparently influences the development of a completely crossed projection.